1. Field of the Invention
The present invention relates to a grinder wheel for a liquid crystal display device, and more particularly, to a grinder wheel for a liquid crystal display device for cutting liquid crystal display panels fabricated on a large mother substrate into separate unit liquid crystal display panels to grind unit liquid crystal display panels and a method of fabricating a liquid crystal display (LCD) device using the same.
2. Description of the Related Art
Recently, with increasing interest in information displays and request for using portable information media, thin and light flat panel displays (FPD) that replace cathode ray tubes (CRT) that are conventional displays have been studied and commercialized. In particular, among the FPDs, LCD device displays images using optical anisotropy of liquid crystal and have excellent resolution, color display, and picture quality to be actively applied to notebooks and desktop monitors.
Hereinafter, the LCD device will be described in detail.
A common LCD device is composed of a liquid crystal display panel including a driving circuit unit, a back light unit provided under the liquid crystal display panel to emit light to the liquid crystal display panel, a mold frame that supports the back light unit and the liquid crystal display panel, and a case.
The liquid crystal display panel is composed of a color filter substrate, an array substrate, and a liquid crystal layer formed between the color filter substrate and the array substrate.
The color filter substrate is composed of a color filter composed of red (R), green (G), and blue (B) sub-color filters, black matrix provided among the sub-color filters to intercept the light that passes through the liquid crystal layer, and transparent common electrodes that apply a voltage to the liquid crystal layer.
The array substrate is composed of a plurality of gate lines and data lines vertically and horizontally arranged on the substrate to define a plurality of pixel regions, thin film transistors (TFT) that are switching devices formed in the regions where the gate lines intersect the data lines, and pixel electrodes formed on the pixel regions.
The array substrate and the color filter substrate of the above-described structures are attached to each other by a sealant formed in the outline of an image display region to face each other so that the liquid crystal display panel is obtained. The two substrates are attached to each other by an attachment key formed in the array substrate or the color filter substrate.
In general, according to a liquid crystal display device, in order to improve yield, TFT array substrates are formed on a large mother substrate, color filter substrates are formed on another mother substrate, and then the two mother substrates are attached to each other to simultaneously form a plurality of liquid crystal display panels. At this time, a process of cutting the liquid crystal display panels into a plurality of unit liquid crystal display panels is required.
In general, the unit liquid crystal display panels are cut by forming scribing grooves on the surface of the mother substrate using a wheel whose hardness is larger than the hardness of glass so that crack is transmitted along the scribing grooves. Such a liquid crystal display panel will be described in detail with reference to the attached drawings.
FIG. 1 schematically illustrates the structure of the section of liquid crystal display panels obtained by attaching a first mother substrate on which TFT array substrates are formed and a second mother substrate on which color filter substrates are formed to each other.
As illustrated in FIG. 1, the unit liquid crystal display panels are formed so that one side of each of TFT array substrates 1 is longer than one side of each of color filter substrates 2. This is because gate pad units (not shown) and data pad units (not shown) are formed at the edges of the TFT array substrates 1 that do not overlap the color filter substrates 2.
Therefore, the color filter substrates 2 formed on the second mother substrate 30 are separated from each other by a first dummy region 31 corresponding to the area by which the TFT array substrates 1 formed on the first mother substrate 20 are longer than the color filter substrates 2.
Also, the unit liquid crystal display panels are properly arranged to maximally use the first and second mother substrates 20 and 30. In general, the unit liquid crystal display panels are separated from each other by a second dummy region 32, which vary with a model.
After the first mother substrate 20 on which the TFT array substrates 1 are formed and the second mother substrate 30 on which the color filter substrates 2 are formed are attached to each other, the liquid crystal display panels are cut into unit liquid crystal display panels. At this time, the first dummy regions 31 by which the color filter substrates 2 of the second mother substrate 30 are separated from each other and the second dummy regions 32 by which the unit liquid crystal display panels are separated from each other are simultaneously removed.
After cutting the liquid crystal display panels from the second mother substrate 30, the sharp edges of the unit liquid crystal display panels are ground so that it is possible to prevent the short wiring lines formed at the edges of the TFT array substrates 1 in order to intercept static electricity that can be generated when a conductive film is formed on the TFT array substrates 1 from being removed, to prevent pieces from being broken out of the edges of the unit liquid crystal display panels due to external shock, and to prevent a worker from being damaged by the sharp edges of the unit liquid crystal display panels during processes.
That is, as illustrated in FIG. 2, protrusion ends 40 that protrude outside are formed on the sides of the array substrates 1 and the color filter substrates 2 that are cut by shock. The protrusion ends 40 are commonly generated in all parts where the scribing grooves intersect each other.
The protrusion ends 40 are removed using a grinder wheel. FIG. 3 is a plan view schematically illustrating the structure of a common grinder wheel.
As illustrated in FIG. 3, in a grinder wheel 70, a grinder surface 74 is formed at the edge of the top surface of a disk-shaped grinder device 71.
A hole 77 is formed in the center of the grinder wheel 70 in order to load the grinder device 71 in the spin of a motor.
In general, the grinder wheel 70 including one grinder surface 74 is used for a process of grinding liquid crystal display panels. When the liquid crystal display panels are ground by one grinder surface 74, since the same grinder surface 74 must be continuously used, the life of the grinder wheel 70 is reduced. Also, since the area of the protrusion end (40 of FIG. 2) that contacts the grinder wheel 74 is small during high speed grinding, the part that is not ground exists.
Also, when the grinder wheel 70 is used for a long time, the specific part of the grinder surface 74 is abraded so that grinding quality deteriorates since the same part is continuously used.